1. Field of the Invention
The present invention relates to a projector and more particularly to the structure thereof.
2. Description of the Prior Art
Conventionally known is a projector which comprises electro-optical devices for forming an optical image of a light beam emitted from a light source in accordance with image information and a projection lens for expanding and projecting the image formed by the electro-optical devices. The projector of this type has been widely used for multi-media presentation in a conference, an academic meeting, or an exhibition.
More particularly, such a projector has a color beam splitting optical system interposed between the light source and the electro-optical devices. The color beam splitting optical system is accommodated in an optical component housing (inner case) designed to block ambient light, being adapted to split a light beam from the light source into beams of three colors (red, green, and blue) and then transmit the respective color beams to the electro-optical devices. Then, three color images of the respective color beams formed in the electro-optical devices are transmitted to a color beam combining optical system (prism) to be combined into a color image, thereafter being expanded and projected via the projection lens supported by a metallic support member (a head body).
The projector of this type may be kept installed in a conference room for making a presentation. However, it is often carried therein as required, or carried therefrom after a presentation to be stored somewhere else. Accordingly, it is necessary to improve the portability of the projector for ease of carrying it and thus it has been desired to reduce the size and weight of the projector.
However, a conventional projector is provided with a inner case in each of the upper and lower cases to accommodate and fix various types of optical components, in order to prevent shift of the optical axis of the optical components caused by considerable heat generated by the light source portion, the color beam combining optical system, the power supply unit and so on. However, this configuration is a stumbling block in the way of reducing the size and weight of the projector.
There is also another problem with the conventional projector. That is, it is difficult to take measures against EMI (Electro-Magnetic Interference) since circuits for processing feeble video signals at high speed and a light-source lamp causing strong noise are accommodated together in a narrow space.
The present invention was developed in view of these problems. Accordingly, it is an object of the present invention to provide a projection display system which is further reduced in weight and size and which gives sufficient consideration to the countermeasures against EMI.
The present invention provides a projector having vertically separable outer cases which accommodate an optical system comprising a color beam splitting optical system for splitting light from a light source into beams of predetermined colors; an electro-optical device for modulating the color beams split by the color beam splitting optical system in accordance with image information; a color beam combining optical system for combining the color beams modulated by the electro-optical device; and a projection lens for projecting a resultant beam combined by the color beam combining optical system. The system is characterized in that optical components constituting the optical system are attached to a inner case. In addition, the inner case is fixed to one of the outer cases so as to accommodate at least the color beam splitting optical system in a enclosure constituted by the inner case and the one of the outer cases.
This allows the optical system to be constituted using one inner case, thereby making it possible to reduce the size and weight of the projector. In addition, air flows into and out of the optical system through an outer case, thereby providing the projector with improved thermal radiation. Furthermore, the inner case and the outer cases are fixed to each other to thereby reinforce each other complementarily, thus making it possible to prevent the positional shift of the optical axis of the optical system caused by aging or the deformation of the components constituting the optical system. From this point of view, it is preferable that the inner case is an integrated box-shaped body with an opening provided on a side.
Furthermore, the projection lens attached to the inner case facilitates the alignment of the optical axis of the optical system with that of the projection lens with ease and high accuracy.
Furthermore, a thermal insulation material interposed between the inner case and the outer case for accommodating the color beam splitting optical system makes it possible to prevent heat conduction from the optical system to the outer case.
Furthermore, the projector is characterized in that a prism is attached to the inner case, the prism constituting the color beam combining optical system. This can obviate the need of the special prism attachment member that has been conventionally used.
The projector is also characterized in that a recessed portion is formed adjacent to the projection lens on a top outside of the inner case, and the electro-optical device and the prism constituting the color beam combining optical system are arranged in the recessed portion. This makes it possible to form a flow path of air for cooling the electro-optical device, thereby providing an increased cooling effect. Besides, it is preferable that an air vent is provided near where the prism is attached to the inner case, thereby allowing the electro-optical device to be positively cooled.
Furthermore, the projector is characterized in that a mirror and a lens, constituting the optical systems, are fixed by resilient members. This makes it possible to fix these optical components without being damaged and prevent these components from dropping off when fixing the inner case to the outer cases.
The projector is also characterized in that a cable for electrically connecting the electro-optical device to a driver board for controlling the electro-optical device is led out from one side of the electro-optical device on the nearer side to the driver board. This allows the cables to be wired in a simple manner.
The projector is also characterized in that a driver board for controlling the electro-optical device is disposed on the top outside of the inner case. This allows the inner case to block noise generated by the light source and radiant heat from the optical systems. However, if countermeasures have been taken somehow against the noise or radiant heat, it is possible to arrange the driver board on the outer case, being integrated with the inner case, for accommodating the color beam splitting optical system.
Besides, it is possible to increase the packing density of components by forming a notched portion in the driver board and by accommodating a fan for cooling the electro-optical device in the notched portion.
It is also preferable to provide the outer cases, being integrated with the inner case, for accommodating the color beam splitting optical system with functions of positioning and supporting the optical components that constitute the optical system. Consequently, this makes it possible to positively position and stably hold each of the optical components. It is also possible to fix the optical components firmly with ease by fixing the inner case and the outer case for accommodating the color beam splitting optical system to each other with screws.
The projector is also characterized in that part of a housing for holding the light source is placed on an outer surface of the outer case, and the housing is made attachable to or detachable from the outer case by using the part of the housing. This makes it possible to replace the light source in conjunction with the housing, thereby facilitating the replacement of the light source. Besides, it is possible to prevent a spark between the housing and the light source by forming the housing of a resin.
It is also possible to provide further increased insulation against the light source by applying an insulation coating to a portion opposite to the light source in the inner case. This is particularly effective in the case where a high-intensity light source is employed.
Besides, it is preferable that the inner case and the outer cases of the present invention are formed of a resin or metal. For resin, there is an advantage of being light in weight and facilitating shaping and finishing. On the other hand, the high material strength of metal makes it possible to provide stabilized accuracy in size and a reduction in thickness to thereby provide a reduction in weight.